How important is the physicochemical interaction in the flocculation of yeast cells?

Hamersveld, E. H. van; Loosdrecht, M.C.M. van; Luyben, K. Ch. A. M.

doi:10.1016/0927-7765(94)80031-6

Cited by 15 publications

(8 citation statements)

References 23 publications

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“…Because the bond strength was not measured, it was also estimated by the model. The collision efficiency is a constant, in case of yeast flocculation, and had a value of 1.0 × 10 −3 , the erosion rate constant was 2.0 × 10 4 m −2 , and the bond strength was 0.25 × 10 −9 N. The latter value is of the same order of magnitude as measured earlier with the same yeast strain (Van Hamersveld et al, 1994).…”

Section: Simulation Resultsmentioning

confidence: 96%

Modeling brewers' yeast flocculation

Hamersveld

Lans

Caulet³

et al. 1998

Biotechnol. Bioeng.

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Section: Simulation Resultsmentioning

confidence: 96%

Modeling brewers' yeast flocculation

Hamersveld

Lans

Caulet³

et al. 1998

Biotechnol. Bioeng.

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“…Cell surface hydrophobicity has been considered by some authors as one of the major factors responsible for the flocculation of brewing yeast (Straver et al, 1993;Straver and Kijne, 1996) and flocculin, a hydrophobic proteinaceous cell surface factor, was identified (Smit et al, 1992). However, other studies contradicted the importance of hydrophobic interactions (Suzzi et al, 1994;van Hamersveld et al, 1994). Despite the extensive research that has been undertaken, the molecular basis and the exact mechanism of yeast flocculation is still not completely understood.…”

Section: Introductionmentioning

confidence: 94%

“…This approach was applied here, using a cell radius of 3 Am, dielectric constant of 78.5 (pure water), an estimated Hamaker constant of 0.8 kT for biological particles in water (Nir, 1977;van Hamersveld et al, 1994), ionic strength of 10 mM, and zeta potentials of cells (À12 mV) and spent grain particles (À5 mV) at the pH of the continuous fermentation (f3.4). The small potential energy barrier between a brewing yeast cell and a spent grain particle (9 kT) at 3 nm indicates the possibility of the capture of the cell in close contact with the carrier (Fig.…”

Section: Cell-carrier Adhesionmentioning

confidence: 99%

Physicochemical surface properties of brewing yeast influencing their immobilization onto spent grains in a continuous reactor

Branyik

Vicente

Oliveira

et al. 2004

Biotech & Bioengineering

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Immobilization of brewing yeast onto a cellulose-based carrier obtained from spent grains, a brewing byproduct, by acid/base treatment has been studied in a continuously operating bubble-column reactor. The aim of this work was to study the mechanisms of brewing yeast immobilization onto spent grain particles through the information on physicochemical surface properties of brewing yeast and spent grain particles. Three mechanisms of brewing yeast immobilization onto spent grains carrier were proposed: cell-carrier adhesion, cell-cell attachment, and cell adsorption (accumulation) inside natural shelters (carrier's surface roughness). The possibility of stable cell-carrier adhesion regarding the free energy of interaction was proved and the relative importance of long-range forces (Derjaguin-Landau-Verwey-Overbeek theory) and interfacial free energies was discussed. As for the cell-cell attachment leading to a multilayer yeast immobilization, a physicochemical interaction through localized hydrophobic regions on cell surface was hypothesized. However, neither flocculation nor chain formation mechanism can be excluded so far. The adsorption of brewing yeast inside sufficiently large crevices (pores) was documented with photomicrographs. A positive effect of higher dilution rate and increased hydrophobicity of base-treated spent grains on the yeast immobilization rate has also been found.

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“…The most generally accepted mechanism is one mediated by lectins, which recognize mannan receptors on adjacent cells and require the presence of calcium (28, 33-35, 37, 57). van Hamersveld et al (65) found that the net interaction energy of flocculated brewer's yeast was much higher than could be expected on the basis of nonspecific (van der Waals and electrostatic) interactions only. However, the involvement of a molecular recognition mechanism does not mean that nonspecific interactions are negligible: the specific binding can be revealed only if there is a nonspecific repulsion (5).…”

mentioning

confidence: 95%

Mechanisms of yeast flocculation: comparison of top- and bottom-fermenting strains

Dengis

Nélissen

Rouxhet

1995

Appl Environ Microbiol

102

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The flocculation of two brewing yeast strains, top-fermenting strain Saccharomyces cerevisiae MUCL 38485 and bottom-fermenting strain Saccharomyces carlsbergensis MUCL 28285, has been investigated by means of a turbidimetric test. The two strains showed different electrical properties, a different hydrophobicity, and a different surface chemical composition. They flocculated according to completely different mechanisms; however, no correlation between the cell physicochemical properties and the onset of flocculation was found for either strain. Flocculation of the bottom strain was governed by a lectin-mediated mechanism. It was inhibited by mannose and some other sugars, required calcium specifically, occurred in a narrow pH range different from the isoelectric point, and was not influenced by ethanol. The onset of flocculation at the end of the exponential phase was controlled both by the appearance of "active" lectins at the cell surface and by the decrease in sugar concentration in the solution. Flocculation of the top strain was not inhibited by mannose, did not require the addition of calcium, and took place at the cell isoelectric point. Low concentrations of ethanol broadened the pH range in which the cells flocculated, and flocculation was favored by an increase of ionic strength. Adsorbed ethanol may induce flocculation by reducing the electrostatic repulsion between cells, by decreasing steric stabilization, and/or by allowing the protrusion of polymer chains into the liquid phase. The onset of flocculation was controlled by both a change of the cell surface and an increase in ethanol concentration. The only evidence for an adhesin-mediated mechanism was the specific requirement for a small amount of calcium.

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How important is the physicochemical interaction in the flocculation of yeast cells?

Cited by 15 publications

References 23 publications

Modeling brewers' yeast flocculation

Modeling brewers' yeast flocculation

Physicochemical surface properties of brewing yeast influencing their immobilization onto spent grains in a continuous reactor

Mechanisms of yeast flocculation: comparison of top- and bottom-fermenting strains

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